Synthesis and film formation of iron–cobalt nanofibers encapsulated in graphite shell: magnetic, electric and optical properties study

Abstract

Novel characteristics for the Fe_xCo_y alloys have been obtained when these compounds were synthesized in the form of nanofibers encapsulated in a graphite shell. The prepared nanofibers reveal good semiconducting features as a thin film from the prepared nanofibers supported on a graphite disk and could be utilized as a diode with good rectifying behaviour. Magnetic properties study showed that the introduced nanofibers are magnetically clean as very low remanent magnetizations were detected; moreover the saturation magnetization is a temperature-independent property. Optical properties study indicated that these nanofibers have band gap energies of 4.73 and 5.43 eV. Fe_xCo_y bimetallic alloys could be produced in the form of nanofibers encapsulated in a graphite shell by calcination of electrospun nanofiber mats composed of poly(vinyl alcohol), ferrous acetate and cobalt acetate tetrahydrate in an argon atmosphere at 750 °C. The composition of the nanofibers could be adjusted by controlling the concentration of the original electrospun solution; two formulations have been prepared: FeCo and FeCo_2.7. Transmission electron microscopy indicated that the thickness of the graphite shell enveloping the obtained nanofibers is ∼10 nm. A graphite disk possessing on its surface a well attached thin film from the introduced nanofibers could be successfully prepared when a diskette made of poly(acrylonitrile) was used as a collector during the electrospinning process. The introduced methodology is effective, simple and can be exploited to produce different metallic alloys nanofibers.